s390: avoid reaching into memory core internals

[qemu.git] / iov.c

diff --git a/iov.c b/iov.c
index b3330610bba4fb1e72f3f87266e6fa8bec6da19a..c6a66f0afe2a584e8af548d1601016ee8b6d513d 100644 (file)
--- a/iov.c
+++ b/iov.c
@@ -26,7 +26,7 @@
 # include <sys/socket.h>
 #endif
 
-size_t iov_from_buf(struct iovec *iov, unsigned int iov_cnt,
+size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
                     size_t offset, const void *buf, size_t bytes)
 {
     size_t done;
@@ -146,6 +146,13 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt,
 {
     ssize_t ret;
     unsigned si, ei;            /* start and end indexes */
+    if (bytes == 0) {
+        /* Catch the do-nothing case early, as otherwise we will pass an
+         * empty iovec to sendmsg/recvmsg(), and not all implementations
+         * accept this.
+         */
+        return 0;
+    }
 
     /* Find the start position, skipping `offset' bytes:
      * first, skip all full-sized vector elements, */